Radiation-induced polyene formation of poly(vinyl chloride). I. Effect of conformations

PVC samples with different syndiotacticities were degraded at temperatures in the range of 10° to 115°C by UV radiation. The average length of polyenes increases with increase in syndiotacticity of PVC. It was found that by comparison with the long tactic sequences, on the basis of Bernoullian statistics, the propagation reaction of the polyenes at room temperature is terminated when there are more than three racemic dyads in the tactic sequences. At room temperature, the deformation of about 1.3 Å of the PVC main chain takes place, and at temperatures above the glass transition temperature the propagation rate of the polyenes is competitive with the relaxation time between the (tt) and the (tg) conformations.